cLoops2: a full-stack comprehensive analytical tool for chromatin interactions

Investigating chromatin interactions between regulatory regions such as enhancer and promoter elements is pivotal for a deeper understanding of gene expression regulation. The emerging 3D mapping technologies focusing on enriched signals such as Hi-TrAC/Trac-looping and HiChIP, compared to Hi-C, reduce the sequencing cost, and provide higher interaction resolution for cis-regulatory elements and more comprehensive information such as chromatin accessibility. A robust pipeline is needed for the comprehensive interpretation of these data, especially for loop-centric analysis. Therefore, we have developed a new versatile tool named cLoops2 for the full-stack analysis of the 3D chromatin interaction data. cLoops2 consists of core modules of peak-calling, loop-calling, differentially enriched loops calling and loops annotation. Additionally, it also contains multiple modules to carry out interaction resolution estimation, data similarity estimation, features quantification and aggregation analysis, and visualization. cLoops2 with documentation and example data are open source and freely available at GitHub: https://github.com/YaqiangCao/cLoops2 Overall design: ChIC-seq data in GM12878 for antibodies of IgG, CTCF, H3K4me3 and H3K27ac were generated to benchmark cLoops2 peak-calling performance.